Drum support for steam boiler



Aug. 2, 1966 J KUREK, JR 3,263,656

DRUM SUPPORT FOR STEAM BOILER filed Feb. 18, 1964 2 Sheets-Sheet 1 I INVENTOR.

JOHN KUREK,JR.

AGENT 2, 1966 J. KUREK, JR 3,263,656

DRUM SUPPORT FOR STEAM BOILER Filed Feb. 18, 1964 2 Sheets-51mm; 2

IOL

INVENTOR. JOHN KUREK, JR.

BY fi/za (Q29 AGENT United States Patent ice 3,263,656 DRUM SUPPORT FOR STEAM BOILER John Kurek, Jr., Simsbury, Conn., assignor to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed Feb. 13, 1964, Ser. No. 345,611 9 Claims. (Cl. 122510) This invention relates to steam boilers which are suspended from overhead structural steel, and is more particularly concerned with supporting by means of drum hangers a portion of the boiler including the steam and water drum and the tubes connected thereto as well as other equipment attached to the tubes such as boiler casing.

In large modern steam generators operating at high pressures the temperature of the drum and tubes reaches a relatively high value. This results in substantial displacement of the drum due to thermal expansion of the drum and the tubes. Often the load carried by the drum hangers exceeds one million pounds. Since the pressure at which many modern steam generators are operating approaches the critical pressure of 3206 lb./sq. in., the temperature of the steam contained in the drum and the tubes may exceed 700 F. Thermal expansion of these boiler parts, therefore, may often amount to several inches. This displacement of the drum relative to the overhead supporting steel imposes a considerabl bending stress on the hanger rod, in addition to the tensional stress due to load. Accordingly, hanger rods of as much as 7 inch diameter must be used to carry these loads. In large boilers generating more than one million pounds of steam per hour the overhead supporting steel may be at an elevation of 30-40 feet above the drum elevation. However, steel rods are not commercially available of the diameter and length required to make the drum hanger out of one piece. Accordingly, to fabricate the drum hanger, several pieces of steel rod must be joined by welding. Because of the large diameter this requires an expensive welding procedure. Furthermore, maintaining uniform temperatures during welding and cooling of these welds is diificult.

In boilers of moderate size and where the load carried by the drum hanger is not unusually high excessive bending stresses in the hanger rod are avoided by suspending the drum hanger from rocker plates having a rounded bearing surface. However, measurements on actual installations have shown that the rocker plates are only about 50% effective in reducing the bending stress in the drum hanger. It was found, as the load increases that the bearing surface of the rocker digs into the surface of the underlying bearing plate, reducing and eventually preventing effective roller action.

It is accordingly an object of the invention to provide a drum hanger having a cross section which is subject to a relatively low outer fibrous stress due to bending forces caused by thermal expansion .of the boiler parts.

It is another object of the invention to provide a drum hanger that is being fabricated by joining commercially available rod lengths by welding and wherein such welded joints have a cross sectional configuration which can be more easily welded and more effectively X-rayed for quality control of the Weld.

Other objects and advantages of the invention will become apparent from the following description of an illus- 3,263,656 Patented August 2, 1966 trative embodiment thereof when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a partial elevational cross section of a steam generator being suspended from overhead steel;

FIG. 2 is a plan view of the steel drum and supports and showing the directions in which the drum ends tend to move due to thermal expansion;

FIG. 3 is an enlarged plan view of the steam drum and drum hangers, when taken on line 3-3 of FIG. 4;

FIG. 4 is an elevational cross section of the steam drum and support when taken on line 44 of FIG. 3;

FIG. 5 is a portion of a conventional circular drum hanger rod showing the welded joint thereof;

FIGS. 6, 7 and 8 show a portion of a drum hanger rod having an elongated cross section and showing the welded joint thereof;

FIG. 9 illustrates a number of other elongated cross sections which could be used in practicing the invention; and

FIGS. 10 and 11 show another design of drum support to which the invention could b applied with great benefit. Referring now to the drawings wherein like reference characters are used throughout to designate like elements, the illustrative and preferred embodiment of the invention depicted therein includes a vapor generator designated generally as 10 and comprising a furnace chamber 12 lined with heat absorbing tubes 14 and including roof tubes 16 which terminate in a steam and Water drum 18. This drum is suspended from overhead steel 20 by means of drum hangers 22 engaging drum 18 at either end 24 as shown in FIG. 2. The steam generator is restrained by the surrounding steel work in such a manner that a fixed point 25 of zero horizontal expansion is created which point preferably is located approximately midway between front and rear of the boiler and at the centerline 26 thereof.

In a top supported steam generator such as that illustratively depicted in FIG. 1 a major portion of the vertical thermal expansion occurs downwardly from the center of drum 18. Thermal horizontal expansion of the tubes such as roof tubes 16 proceeds from point 25 toward drum 18 and thermal horizontal expansion of the drum proceeds from centerline 26 toward each end 24 of drum 18. The resultant direction of expansion for displacement of drum ends 24 accordingly takes place along lines 28 and away from point 25, the point of zero expansion is indicated in FIG. 2.

Referring now to FIG. 4, drum hanger 22 comprises a lower part 30 which takes a semi-circular shape adapted to cradle drum 18. One of a pair of straight rod lengths 32 extends from either end thereof to form a U-shaped drum hanger. Rod 32 is threaded at its upper end to receive nuts 34 which rest on a bearing plate 36. This plate in turn transfers the load onto structural steel members 20.

In conventional designs the drum hanger is fabricated of round bar stock. The heavy loads imposed on these hangers call for diameters as large as 7 /2 inch, as earlier noted. Because the unusual length required cannot be procured commercially, one or more welded butt joints are therefore needed in the fabrication of the drum hanger. As illustrated in FIG. 5, the large circular cross section of these welded connections make it especially diflicult and costly to produce a good weld. Furthermore, since quality control thereof by X-raying is cumbersome and expensive, this welding procedure is presently undesirable.

Moreover, the heavy loads carried by the drum hanger and imposed on bearing plates 36 cause some yielding of the metal of the rocker and the bearing plate which would reduce the rocker effectiveness. Accordingly, large bending stresses are imposed on the hanger rod in addition to tensional stresses due to load. Because of the large diameter the outer fibres of the circular rod are severely stressed. This together with the difficulties introduced by the welded joints creates a problem of great concern to the boiler manufacturer.

In accordance with the invention this problem has been successfully solved by changing the cross section of the hanger rod where bending stresses occur, from a circular cross section to a cross section of elongated, preferably rectangular configuration, as shown in FIGS. 6, 7 and 8. The area of the rectangular cross section 27 of the upper part of the U-hanger is made approximately equal to the area of the circular cross section of the lower part thereof. Thus in a recent design, the required circular cross section of 6% inch diameter of the lower semi-circular portion, resulted in a rectang-ular cross section inches wide and 2% inches deep which cross section is applied to that portion of the drum hanger subjected to bending stresses.

As illustratively shown in FIG. 3 the elongated cross section is located in such a manner that the wide side thereof faces in the direction in which the drum ends 24 move as indicated by lines 28. Greatest flexibility is therefore obtained when bending the rod in the direction of the resultant expansion line 28 without unduly stressing the outer fibres of the cross section.

Other elongated bearing shapes could be used in fabricating the hanger, such as those illustrated in FIG. 9 and the same or similar beneficial results would thereby be obtained.

Also, the invention could be applied to a drum support which consists of only one rod at each end of the drum as is illustratively shown in FIGS. 10 and 11. In this embodiment lug 40 is attached to drum 18 such as by welding. A rod 42 which preferably has a rectangular cross section engages lug 40 such as by welding in the field and transfers the weight of the drum 18 to structural steel supports 20 in a manner as earlier described in connection with FIGS. 3 and 4. Rod 42 is oriented so that the wide side of the rectangular cross section thereof faces expansion line 28.

While I have illustrated and described two preferred embodiments of my invention, it is to be understood that such are merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

Iclaim:

1. In combination, an elongated cylindrical vessel, a hanger for supporting said vessel, means associated with said vessel, said means when exposed to heat being subject to thermal forces tending to move said vessel in a direction which lies in the horizontal plane passing through the longitudinal axis of said vessel and is at an acute angle with respect to said longitudinal axis, said hanger comprising a lower part organized to move with said cylindrical vessel; an upper part suspended from a fixed point of support spaced above said vessel, with said vessel tending to be displaced relative to said fixed point of support, a portion of said hanger having an elongated cross section with the width of said cross section being substantially wider than the depth thereof, and with said depth extending in said direction, to provide a hanger having a low resistance against flexing in said direction, and a high resistance against flexing transversely to said direction.

2. A combination as defined in claim 1 wherein the configuration of said cross section is a rectangle having a width to depth ratio of at least 3 to 1.

3. In combination, an elongated cylindrical vessel, a U-shaped hanger for supporting said vessel, means associated with said vessel, said means when exposed to heat being subject to thermal forces tending to move said vessel in a direction which lies in the horizontal plane passing through the longitudinal axis of said vessel and is at an acute angle with respect to said longitudinal axis, said hanger comprising a lower part having a semi-circular configuration of suitable diameter to serve as a cradle for said cylindrical vessel; two upper parts one extending from each end of said semi-circular configuration to form a U-shaped hanger, a portion of each of said extension parts having an elongated cross section with the width of said cross section being at least three times the depth thereof, and with said depth extending in said direction, to provide a hanger having a low resistance against flexing in said direction, and a high resistance against flexing transversely to said direction.

4. A combination as defined in claim 3 wherein the configuration of said cross section is a rectangle.

5. In combination, an elongated cylindrical vessel, a hanger for supporting said vessel, means associated with said vessel, said means when exposed to heat being subject to thermal forces tending to move said vessel in a direction which lies in the horizontal plane passing through the longitudinal axis of said vessel and is at an acute angle with respect to said longitudinal axis, said hanger comprising a lower part fixedly attached to said cylindrical vessel; an upper part attached to a fixed point of support spaced above said vessel, with said vessel tending to be displaced relative to said fixed point of support, a portion of said hanger having an elongated cross section with the width of said cross section being substantially wider than the depth thereof, and with said depth extending in said direction, to provide a hanger having a low resistance against flexing in said direction, and a high resistance against flexing transversely to said direction.

6. A combination as defined in claim 5 wherein the configuration of said cross section is a rectangle having a width to depth ratio of at least 3 to 1.

7. In a steam boiler, a furnace chamber having a roof lined with parallelly arranged heat absorbing tubes, a steam drum extending across the width of said furnace chamber adjacent one end of said roof, said roof tubes being connected to said drum with the longitudinal axis of said tubes extending transversely to the longitudinal axes of said drum, said tubes and said drum being subject to thermal expansion along their respective longitudinal axes; means for fixedly supporting said tubes at a distance remote from said drum; hanger means for yieldingly supporting said drum from a fixed point spaced above said drum; said thermal expansion of said tubes and drum tending to move said drum relative to said fixed point in a resultant direction; a portion of said hanger means having an elongated cross section with the width of said cross section being substantially wider than the depth thereof, and with said depth extending in said resultant direction, to provide a hanger means having a low resistance against flexing in said resultant direction and a high resistance against flexing transversely to said resultant direction.

8. In a steam boiler, a furnace chamber having a roof lined with parallelly arranged heat absorbing tubes, a steam drum extending across the width of said furnace chamber adjacent one end of said roof, said roof tubes being connected to said drum with the longitudinal axis of said tubes extending transversely to the longitudinal axes of said drum, said tubes and said drum being subject to thermal expansion along their respective longitudinal axes; means for fixedly supporting said tubes at a distance remote from said drum; a U-shaped hanger for yieldingly supporting said drum from a fixed point spaced above said drum; said thermal expansion of said tubes and drum tending to move said drum relative to said fixed point in a resultant direction; said hanger comprising a lower part having a semi-circular configuration of suitable diameter to serve as a cradle for said cylindrical vessel; two upper parts one extending from each end of said semicircular configuration to form a U-shaped hanger, a portion of each of said extension parts having an elongated cross section with the 'width of said cross section being at least three times the depth thereof, and with said depth extending in said resultant direction, to provide a hanger having a low resistance against flexing in said resultant direction, and a high re- 5 width to depth ratio of at least 3 to 1.

References Cited by the Examiner UNITED STATES PATENTS 1,757,343 5/ 1930 Steinmuller 122-510 2,698,610 1/1955 Longvaud et a1. 122510 2,730,080 1/1956 Stallkarmp 122--478 KENNETH W. SPRAGUE, Primary Examiner. 

1. IN COMBINATION, AN ELONGATED CYLINDRICAL VESSEL, A HANGER FOR SUPPORTING SAID VESSEL, MEANS ASSOCIATED WITH SAID VESSEL, SAID MEANS WHEN EXPOSED TO HEAT BEING SUBJECT TO THERMAL FORCES TENDING TO MOVE SAID VESSEL IN A DIRECTION WHICH LIES IN THE HORIZONTAL PLANE PASSING THROUGH THE LONGITUDINAL AXIS OF SAID VESSEL AND IS AT AN ACUTE ANGLE WITH RESPECT TO SAID LONGITUDINAL AXIS, SAID HANGER COMPRISING A LOWER PART ORGANIZED TO MOVE WITH SAID CYLINDRICAL VESSEL; AN UPPER PART SUSPENDED FROM A FIXED POINT OF SUPPORT SPACED ABOVE SAID VESSEL, WITH SAID VESSEL TENDING TO BE DISPLACED RELATIVE TO SAID FIXED POINT OF SUPPORT, A PORTION OF SAID HANGER HAVING AN ELONGATED CROSS SECTION WITH THE WIDTH OF SAID CROSS SECTION BEING SUBSTANTIALLY WIDER THAN THE DEPTH THEREOF, AND WITH SAID DEPTH EXTENDING IN SAID DIRECTION, TO PROVIDE A HANGER HAVING A LOW RESISTANCE AGAINST FLEXING IN SAID DIRECTION, AND A HIGH RESISTANCE AGAINST FLEXING TRANSVERSELY TO SAID DIRECTION. 